The inventive concept relates generally to semiconductor memory devices, and more particularly, to multi-level cell (MLC) nonvolatile memory devices and related reprogramming methods.
Semiconductor memory devices can be roughly divided into two categories according to whether they retain stored data when disconnected from power. These categories include nonvolatile memory devices, which retain stored data when disconnected from power, and volatile memory devices, which lose stored data when disconnected from power.
Flash memory devices are an increasingly popular form of nonvolatile memory devices. Flash memory devices are widely used to various forms of data (e.g., audio and images) in information appliances such as computers, cellular phones, smart phones, PDAs, digital cameras, camcorders, voice recorders, MP3 players, handheld PCs, game consoles, fax machines, scanners, and printers, to name but a few.
There is a general demand for nonvolatile memory devices, including flash memory, with increased storage capacity and performance, as well as lower power consumption. In an effort to achieve higher storage capacity, researchers have developed nonvolatile memory devices capable of storing more than one bit per memory cell, so called MLC devices. The storage of multiple bits per cell, however, tends to reduce the operating margins of the devices, rendering them susceptible to errors. Accordingly, there is ongoing research into operating methods and device improvements to improve the reliability of MLC devices.